Mocking the Authentication Provider

[Fact]
public void HowToMockAuthenticationProvider()
{
  // create and configure authentication provider mock
  var provider =
    Substitute.For<Sitecore.Security.Authentication.AuthenticationProvider>();

  provider.Login("John", true).Returns(true);

  // switch the authentication provider so the mocked version is used
  using (new Sitecore.Security.Authentication.AuthenticationSwitcher(provider))
  {
    // the authentication manager is called with expected parameters and returns True
    Xunit.Assert.True(
      Sitecore.Security.Authentication.AuthenticationManager.Login("John", true));

    // the authentication manager is called with wrong parameters and returns False
    Xunit.Assert.False(
      Sitecore.Security.Authentication.AuthenticationManager.Login("Robber", true));
  }
}